The use of zeolites as catalysts and/or catalyst carriers has long been recognized and many methods to improve zeolitic base materials have been reported in the art. In the early days of zeolite research and development much attention has been devoted to physically changing the nature and possibly the properties of zeolitic base materials, e.g. by calcining, calcining under so-called selfsteaming conditions or by wet calcination. Also the treatment with ammonium-ions in various stages of the zeolite preparation procedures has been reported extensively.
It has also been reported that zeolites can be modified by treating them with certain metal salt solutions, or even metal salts themselves, in combination with various pre- and after-treatments to ensure that the zeolites are produced in the most active form.
In the course of the development of zeolites it has now been found that zeolites can be modified by treatment with certain metal-ions without requiring pre- or after-treatment with ammonium-ions. Moreover, the crystallinity of the starting material can be substantially maintained during the modification procedure.